1. Field of the Invention
The present invention relates generally to a method for performing three-dimensional (3-D) graphics on a computer and, in particular, to a method of accelerating rendering of 3-D images on a display device of a computer system with no incremental graphics memory requirements.
2. Description of Related Art
Multimedia computer systems often perform operations requiring the integration of rendered 3-D graphic image data and two-dimensional (2-D) graphics image data. A typical example of these operations is a flight simulator, where a 2-D image of the control panel of a simulated cockpit is displayed on one part of the screen and a 3-D rendered image simulating the landscape which would be seen by the pilot sitting in the cockpit is displayed on a separate part of the screen, partially hidden by the 2-D image of the control panel.
As the majority of multimedia computers include windowing systems, these images are displayed either in a window appearing on the screen or covering the entire screen. This scheme is illustrated in FIG. 1. In FIG. 1, a window 110 on display 120 of computer 130 shows an integrated picture 140 including a 2-D portion 150 and a rendered 3-D portion 160.
Since rendering the 3-D portion 160 of the image requires substantially more time than a single CRT frame scan of the display 120, the rendering is performed offline on a separate framebuffer (not shown). A framebuffer is a 2-D memory region whose locations map directly to pixel locations on display 120.
As rendering is a very time consuming operation, there is a need for a method of rendering which reduces the amount of time required to render 3-D image data in interactive applications.